FIG. 9 shows a basic structure of a conventional wire electric discharge machining apparatus described in, for example, Japanese Unexamined Patent Publication No. 4-304927.
In the drawing, reference numeral 2 denotes a fixing table on which a workpiece is fixed and machined. Reference numeral 3 denotes an X-axis guiding mechanism for moving an object placed thereon in an X-direction in the drawing. Reference numeral 4 denotes a Y-axis guiding mechanism for moving an object placed thereon in a Y-direction in the drawing. Reference numeral 5 denotes a wire electrode functioning as an electrode for machining. Reference numeral 6 denotes an automatic wire feeding device (hereinafter referred to as "AF device") provided with an upper wire guide (not shown) at a distal end thereof. Reference numeral 7 denotes a taper cutting device (hereinafter referred to as "T/C device") that enables angled machining. Reference numeral 8 denotes a Z-axis base for moving the AF device 6, etc. in a Z-direction in the drawing. The foregoing components designated by reference numerals 6 through 8 constitute an upper support assembly. Reference numeral 9 denotes a column supporting the Z-axis base 8. Reference numeral 10 denotes a saddle for fixing the Y-axis guiding mechanism 4. Reference numeral 11 denotes a machine base functioning as a base for supporting the entire structure. Reference numeral 12 denotes a lower arm for collecting the wire electrode 5, which has finished machining a workpiece, via a lower wire guide (not shown) provided at a distal end thereof. Reference numeral 13 denotes a machining tank filled with a machining solution to perform machining therein. Reference numeral 14 denotes a lower support assembly to be discussed hereinafter.
FIG. 10 and FIG. 11 show details of a section where the column 9 of the conventional wire electric discharge machining apparatus shown in FIG. 9 is mounted.
In the drawings, reference numeral 4a denotes a guide rail of the Y-axis guiding mechanism 4. Reference numeral 4b denotes a Y-axis guide of the Y-axis guiding mechanism 4 guided by the guide rail 4a. Reference numeral 14 denotes a lower support assembly to which the lower arm 12 is fixed. Reference numeral 15 denotes a bolt for fixing the column 9 and the lower support assembly 14. As is obvious from FIG. 11, the Y-axis guides 4b of the Y-axis guiding mechanism 4 are directly provided at the bottom of the column 9.
However, in the conventional wire electric discharge machining apparatus configured as set forth above, the Y-axis guides 4b of the Y-axis guiding mechanism 4 on which the column 9 and the lower support assembly 14 are mounted and which guides movement in the Y-direction have been directly attached to the column 9 as shown in FIG. 10 and FIG. 11, and they have been installed in a structure separate from the lower support assembly 14 that supports the wire electrode 5 for machining a workpiece. This has been posing a problem in that it is extremely difficult to obtain squareness between the lower support assembly 14 and the lower arm 12 and the mounting surface of the Y-axis guiding mechanism 4 in an assembly process.
Furthermore, in the conventional wire electric discharge machining apparatus, since the column 9 and the lower support assembly 14 have been separated as illustrated in FIG. 10 and FIG. 11, there is no structure for supporting the lower support assembly 14; therefore, in an assembly process, the lower support assembly 14 must be first fixed to the column 9 by the bolt 15, then the lower arm 12 and the Y-axis guides 4b must be installed. Hence, the lower support assembly 14 cannot be independently installed, leading to poor assemblability and low work efficiency. On the other hand, if the components disposed from the column 9 to the lower support assembly 14 are integrated, there has also been a problem that it is difficult to machine it because the structural member becomes excessively large.